Unsaturated compounds under goes addition reaction to produce saturated compounds..
In the equation given above i.e
H2C=CH2 + F–F —> FCH2CH2F
we can see that the double in H2C=CH2 disappear by the reaction of F–F to produce FCH2CH2F which has no double. This simply indicates that the F–F was added to H2C=CH2. Hence, the reaction is called addition reaction.
